Electrical recordings from the auditory cortex of 15 people identified brain cells that specifically respond when we listen to singing
Humans may have neurons whose main job is to process singing. Scientists have previously found neurons that are selective for speech and music, suggesting that our brains have specific cells that handle different types of sounds we hear.
Sam Norman-Haignere at the University of Rochester, New York, and his colleagues recorded brain electrical activity from 15 people while they listened to 165 different sounds. These included music, speech, animal calls and the sound of a flushing toilet.
The participants already had electrodes implanted into their heads, as they were in hospital for epilepsy treatment, which enabled the researchers to get more precise data compared with functional magnetic resonance imaging (fMRI) scans.
With these recordings, the researchers discovered a population of neurons that seemed to respond nearly exclusively to singing, although they also had a very small response to speech and instrumental music.
“This work suggests there’s a distinction in the brain between instrumental music and vocal music,” says Norman-Haignere, although the researchers didn’t test whether the neurons also responded to spoken word or rap music.
They overlaid these results with fMRI data from 30 other people who listened to the same sounds so that they could map the neurons to a specific region of the brain. The “singing” neurons were located roughly between the music and speech-selective areas of the auditory cortex.
The researchers don’t know why we would have such neurons. “It could have been due to some evolutionary role,” says Norman-Haignere. “Many people think that singing has some important role in the evolution of music.”
“But it’s also totally possible that it’s all driven by exposure,” he says. “People spend a huge amount of time listening to music.” The team is confident that these neurons aren’t driven by musical training and that we all probably have them.
“To be able to distinguish the musical properties of sounds is fundamental for survival,” says Jörg Fachner at Anglia Ruskin University in Cambridge, UK. “It makes sense that this dispositional ability is wired into our auditory cortex.”
“It may also explain why singing a beloved song to a person with dementia may allow responses [even though] the neurodegenerative process has limited the functionality of brain areas,” he says. “This result, along with other neuroimaging-related results of musical memory, may help to explain why songs may help dementia patients.”
Journal reference: Current Biology, DOI: 10.1016/j.cub.2022.01.069
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